Revision Knee Replacement
What is Revision Knee Replacement?
If you have had a knee replacement, and it is no longer functioning or alleviating your symptoms, you may require further surgery. This is called a revision knee replacement operation. All forms of knee replacement surgery have a finite lifespan. The chance that a total knee replacement lasts 15 years is 85% and a unicompartmental knee is 60 to 80%.
What causes knee replacements to wear out?
There are many reasons why a knee replacement may wear out or ‘fail’. In the case of a unicompartmental knee replacement, this may occur from progression of arthritis in other areas of the knee causing pain. Other reasons include loosening of the implants from the bone, wearing out of the plastic liner (polyethylene), the knee feeling unstable, or a pain that has not been relieved by the unicompartmental knee device. Sometimes, an infection may occur that requires removal of the prosthesis and later second operation to convert it to a total knee placement. Total knee replacements may fail for many reasons as well. The most common reason in the 21st century is wearing out of the plastic (polyethylene wear) which can often produce loosening of the implant from the bone (aseptic loosening) or sometimes cysts within the bone (osteolysis). Sometimes knee replacements loosen from bone without the polyethylene wearing out. Other causes of total knee replacement failure are the knee becoming unstable (failure of the supporting ligaments around the knee), stiffness of the knee, problems with the patella such as pain or instability, and infection. Very rarely knee replacements need to be revised on multiple occasions in order to correct the underlying problem. In the case of infection, two or more operations are often required to attempt a successful eradication of the infection.
What happens on the day of your operation?
Undergoing a revision knee replacement is a major operation. You will require all routine investigations that were needed for total knee replacement surgery (blood tests, ECG and other x-rays), as well as specific investigations to establish the cause of failure of your knee replacement. This may include blood tests to exclude infection (ESR, CRP), and possibly a knee aspiration procedure where a needle is introduced into the knee joint to withdraw fluid. There is also another test for infection. Additional specialised x-rays such as a CT scan or even an MRI scan may occasionally be used prior to your surgery.
All patients are reviewed by a medical physician prior to surgery to assess your general fitness for this operation. This is an excellent opportunity to have a full medical assessment and detect any medical issues that can be treated, hence reducing the risk of a medical complication during or after the operation. Prior to your operation, you will be seen by your anaesthetist as well who will discuss the most suitable form of anaesthesia and the other options available to you. In addition, your anaesthetist will discuss the most effective postoperative pain relief measures for you.
What happens on the day of your operation?
You will usually be admitted to hospital the day of your operation, or sometimes the night before. Your surgeon will visit you to answer any questions you may have regarding surgery and will also mark the affected knee with an ink pen.
After your anaesthetic has been administered, a tight band (tourniquet) will be applied to your upper thigh and your leg will be painted with an antiseptic solution. A routine draping will be performed with sterile sheets to allow exposure only of the knee.
A vertical incision is made at the front of your knee that usually includes the previous scar. If multiple scars are present on the front of the knee, the surgeon will choose the safest one to allow adequate exposure of the knee joint. Your surgeon will often send off fluid and tissue from within the knee joint which sometimes helps to establish a cause for failure of the prosthesis. Usually all the failed implants are removed. New specialised knee prostheses are then inserted back onto the end of the femur and to the top of the tibia to recreate a new knee joint. These prostheses are often more sophisticated than those used for routine total knee replacement. This is because stems (rod extensions) that are inside the bone canal are sometimes added in order to allow additional stability of the metal femoral and tibial components.
Before completion of the operation the knee is checked for stability, alignment and degree of motion. Often, a small drain will be left in the knee for 24 hours after the surgery to remove unwanted blood from the knee. Dissolving stitches are usually used to close the wound and the knee is then wrapped in a well padded sterile bandage.
After the operation
You will wake up in the recovery ward where you will be closely monitored until you are ready to return to your ward. Here you will continue to be observed until you are fully awake. Usually, you will spend the first postoperative day in bed. A physiotherapist will visit you to give you breathing exercises for your chest as well as exercises for your leg that can be performed whilst in bed. An x-ray of your knee will be taken to confirm optimal placement of the prosthesis.
Blood thinning medications will be administered daily to reduce the risk of blood clots (DVT) forming in your legs. In addition you will be given special stockings (TEDs) to wear on both of your legs. For the first 24 hours after your operation, an inflatable sleeve will intermittently compress your calves to prevent stagnation of blood flow. You will receive intravenous antibiotics after your surgery for a designated period of time depending on the complexity of the operation. This will help to decrease the risk of infection.
Your bandages will be removed at 48 hours after the operation. A new dressing will be placed over the incision. Your knee will be quite swollen and usually has areas of bruising around it. This is normal. You will be under the daily supervision of a physiotherapist until you are discharged from hospital. The aims of these visits are to optimise motion in the knee, regain ambulation, improve muscle strength and control knee swelling. Once you are mobilising safely, have regained appropriate motion in your knee and your pain is controlled by tablets, you will be able to go home. Some patients require further inpatient care and are transferred to a rehabilitation unit for a short time.
What happens after you go home?
Your rehabilitation will continue after you leave hospital to initially maintain and improve on what you have already achieved. This will take the form of a home exercise program and outpatient physiotherapy visits, which usually last 3-6 months.
An appointment will be made to see your surgeon six weeks after the operation. The goals of your revision knee replacement surgery are to be able to walk independently, to be able to bend your knee and to reduce the pain you were experiencing prior to your surgery.